The present invention has for its object ionic compounds in which the ionic charge is carried by a pentacyclic nucleus or a derivative of tetrazapentalene, and their uses.
Derivatives of non-nucleophilic or slightly basic anions have an increasing importance in all applications of chemistry to stabilize or activate various cationic charges such as those of coloring materials or intermediate species in polymerizations. They also act as intermediates for various reactions of organic chemistry. In electrochemistry, media other than water are more and more relied upon for applications such as primary or secondary generators, supercapacitances, systems of modulation of light. The introduction of a weak ionic conductivity in the usual materials (polymers, combustible liquids), enables to disperse electrostatic charges.
The mainly known derivatives are those derived from coordination anions of the type BF4xe2x88x92, PF6xe2x88x92, AsF6xe2x88x92, however, they have a limited stability due to the dissociation equilibrium releasing the fluoride anion and the corresponding Lewis acid, the two causing parasite reactions and presenting some toxicity. The perchlorate anion ClO4xe2x88x92 is thermally unstable and dangerous.
On the other hand, anions derived from perfluoroalkylsulfonates and especially bis(perfluoroalkylsulfonyl)imides are known, which present interesting properties. However, the chemistry of these compounds is relatively difficult to control, in particular the preparation of precursors of the type RFSO2xe2x80x94. It is also known that hydrocarbons such as cyclopentadiene easily form salts by deprotonation, however, they acidity and the stability of the anion remain very insufficient (pKa≈16).
The inventors have found surprisingly that the properties of compounds derived from cyclopentadiene were considerably modified when a carbon of the cycle was replaced by a more electronegative element than carbon, or when an electronegative substituent was fixed to a carbon atom of the cycle. Depending on the choice of substituents, these compounds give salts which are easily soluble and strongly dissociated, including in organic media which are less polar than water. These salts have interesting properties for a number of applications and their preparation relies on materials which are more easily accessible. It is for example possible to obtain stable anionic heterocycles incorporating smaller quantities, which may even be null, of fluorine, or from fluorinated compounds which are easily accessible.
It is known and particularly interesting to introduce ionic groups in molecules or organic polymers having various functions. Coulombic forces correspond, indeed, to the stronger interactions which are available at the molecular level, and the ionic groups modify in the most noted way the molecules to which they are bonded. Coloring materials which are made soluble in water by means of sulfonate or carboxylate functions may be mentioned. However, the groups of this type xe2x80x94CO2xe2x88x921/mMm+ or xe2x80x94SO3xe2x88x92 1/mMm+ are not dissociated, and they do not induce solubility in solvents other than water or certain highly polar protic solvents such as light alcohols, which considerably restrict the scope of their utilization.
The possibilities of substitution associated with the chemistry of compounds derived from pentagonal cycles of the invention therefore also enable to introduce ionic groups in various molecules.
It is consequently an object of the present invention to provide a family of ionic compounds having a good solubility and good dissociation without having to rely on complex modifications of the starting molecule. The precursors of the molecules of the invention are generally easily accessible.